1. Field of the Invention:
The present invention relates generally to nuclear reactor fuel rod fabrication or assembly apparatus, and more particularly to apparatus, interposed between a vibratory feed bowl type conveyor and a nuclear reactor fuel rod end plug shuttle mechanism, which is capable of properly orienting the nuclear reactor fuel rod end plugs, as the same are randomly delivered by means of the vibratory feed bowl apparatus, so as to eliminate excessive cycling of the end plugs within the vibratory feed bowl apparatus which has conventionally been necessitated in an effort to prevent any jamming or backing-up of the end plugs within the shuttle mechanism or the feed bowl due to the improper orientation of the end plug components, whereby the continuous delivery of the nuclear reactor fuel rod end plugs in a predetermined periodic manner, and in their proper orientation mode, to the shuttle mechanism is facilitated such that the latter can, in turn, convey the end plugs in the particular orientation mode required by the apparatus for assembling together the nuclear reactor fuel rod cladding casings and the nuclear reactor fuel rod end plug components for fabrication of the completed nuclear reactor fuel rods.
2. Description of the Prior Art:
As is well known in the nuclear power plant art, the nuclear reactor core of a typical facility or plant may comprise, for example, at least one hundred or more fuel assemblies, and each fuel assembly, in turn, may comprise, for example, approximately several hundred fuel rods. As an example, a conventional fuel assembly may comprise what is known as a 17.times.17 array of fuel rods, which means that there are seventeen rows or columns of fuel rods, and each row or column contains seventeen fuel rods. Consequently, each fuel assembly would comprise two-hundred eighty-nine fuel rods. In turn, if the reactor core comprised at least one hundred fuel assemblies, it can be readily appreciated that the core would comprise approximately thirty-thousand fuel rods.
The nuclear reactor core fuel pins or fuel rods conventionally comprise thin-walled tubing or cladding within which the fissionable material is housed and supported in a totally encased manner during operation of the reactor. The cladding serves to prevent contact and chemical reactions from occurring between the nuclear fuel and the surrounding environment, such as, for example, the coolant water in a pressurized water reactor (PWR), and of course the cladding additionally serves to confine the radioactive fissionable material therewithin. In order to achieve the aforenoted operational objectives, the cladding must therefore be corrosion resistant, non-reactive, and heat conductive. Conventionally employed materials utilized in the fabrication of the fuel rod cladding include, for example, type 304 stainless steel, or zirconium based alloys, such as, for example, zircaloy-2 or zircaloy-4. The zirconium based alloys are in fact preferable over the stainless steel materials in view of the fact that the zirconium alloys exhibit relatively low capture cross-sections with respect to thermal neutrons.
In accordance with actual conventional fuel pin or fuel rod fabrication techniques, the nuclear fuel, which is usually in the form of cylindrical pellets of uranium dioxide (UO.sub.2) enriched with U-235, is hermetically sealed within the fuel rod cladding or tubing by inserting the fuel within the cladding or tubing and subsequently capping both ends of the cladding or tubing with end plugs or closures which are temporarily attached to the tubing or cladding by means of a force fit. The end plugs are then permanently sealed in position within the tubing or cladding by means of welding operations which are performed, for example, by rotating the tubing relative to an electrode which thereby forms a girth weld at the cladding-plug interfaces, the resulting assemblage of the cladding and end plugs thereby defining the completed fuel rods or pins.
In view of the aforenoted large number of fuel rods which comprise a typical nuclear reactor facility core, and in view of the additional fact that each fuel rod requires two end plugs or closures for its fabrication, it may readily be surmised that the fuel rods are fabricated or assembled in accordance with mass-production techniques which encompass the employment of automatic machinery, peripheral equipment, and assembly apparatus. In particular, in the fabrication of assembled cladding-end plugs fuel rods, the end plugs are conventionally initially deposited en masse within a vibratory bowl type feeder or conveyor wherein, in a conventional manner, the end plugs would be vibrationally conveyed upon a spiral track defined about the periphery of the conveyor until the plugs reached the uppermost track portion at the end of which they would be discharged into, for example, the shuttle mechanism which will operationally interface with the apparatus for inserting the end plugs within the ends of the cladding tubes in preparation for the welding operations. As would often happen, however, the end plugs would be randomly oriented upon the spiral track of the vibratory feed conveyor such that, for example, the longitudinal axes of some of the end plug components would be disposed vertically while the longitudinal axes of some of the other end plug components would be disposed horizontally. The desired orientation mode for the end plug components is the former with their longitudinal axes disposed vertically. In addition, the end plug components have, for example, an upper portion and a lower portion of different diametrical extents whereby an annular shoulder or flange portion is defined at the interface of the two diametrically different portions. This shoulder or flange portion is ultimately disposed in butt contact with the end wall or surface of the fuel rod cladding casing or tube. Consequently, the particularly desired end plugs, from a proper orientation viewpoint, are those with their longitudinal axes disposed vertically, and with the small diameter portions thereof disposed downwardly. This is necessitated in order that the plug components are able to be properly disposed within the shuttle mechanism for, in turn, conveying or transferring the plug components to the apparatus for inserting the end plugs within the cladding tubes or casings. It may therefore be readily appreciated that those plug components which are oriented in modes other than this particularly required mode must be recycled back into the vibratory feed bowl apparatus, or else jamming will occur within the shuttle mechanism should improperly oriented plug components be attempted to be inserted within the shuttle mechanism. Such jamming will of course then lead to backing-up of the plug components within the feed bowl which may necessitate shutting down of the vibratory feed conveyor apparatus. Consequently, conventional vibratory feed bowl apparatus employed in connection with such conveying techniques of the plug components have been provided with plunger or finger type mechanisms which can be activated to deflect improperly oriented plug components back into the vibratory feed bowl for recycling. These conveying techniques, however, have proven to be unacceptable from production goal standpoints in view of the inordinate or excessive amount of cycling time required to achieve a throughput of a predetermined number of plug components for ultimately operationally interfacing with the apparatus for inserting the end plugs within the fuel rod cladding casings.
Accordingly, it is an object of the present invention to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus.
Another object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus which overcomes the various aforenoted disadvantages of conventional nuclear reactor fuel rod fabrication or assembly apparatus.
Still another object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus which will substantially enhance the production rate of assembled nuclear reactor fuel rods.
Yet another object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus which will substantially increase the throughput volume rate of nuclear reactor fuel rod end plugs from vibratory conveyor apparatus to the associated shuttle mechanism.
Still yet another object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus wherein the nuclear reactor fuel rod end plugs are automatically properly oriented for deposition within the shuttle mechanism operationally interfacing with the fabrication or assembly apparatus which inserts the end plugs within the fuel rod cladding casings.
Yet still another object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus wherein the cycling time for the fuel rod end plugs within the vibratory feed conveyor is drastically reduced.
A further object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus wherein the nuclear reactor fuel rod end plugs are automatically properly oriented despite the conveyance of the end plugs to the apparatus of the present invention by means of the vibratory conveyor in a purely random manner.
A still further object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus wherein substantially one-hundred percent of the cycled fuel rod end plugs will be properly oriented so as to continuously deliver the end plugs in a predetermined periodic manner to the shuttle mechanism of the fabrication apparatus.
A yet further object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus which is particularly adapted for handling fuel rod end plugs which are characterized by a diametrical dimension which is greater than the length dimension.
A still yet further object of the present invention is to provide new and improved nuclear reactor fuel rod fabrication or assembly apparatus which will permit passage of the fuel rod end plugs through the apparatus in only one major mode whereby the end plugs will automatically be properly oriented.